The present invention relates to a structure and a method for forming an electro-optics device. More particularly, the present invention relates to a method and a structure for forming a high efficiency electro-optics device.
Many kinds of light emitting diodes are widely in use now. According to the packaging method of the light emitting diodes, there are through-hold light emitting diodes, surface-mounted device light emitting diodes, and flip-chip light emitting diodes, etc.
Referring to FIG. 1, it shows that a cross-sectional view of a conventional light-emitting cell fixed on a die carrier. The light-emitting cell includes mainly an epitaxial structure 10 formed on a substrate 20, and the epitaxial structure 10 consists of at least an n-type semiconductor layer, an active layer, and a p-type semiconductor layer. Due to the progress of the process technologies, in order to increase the light emitting intensity of the light emitting diode, instead of the substrate 20 a transparent substrate is utilized after the epitaxial structure 10 is formed. Thus, the emitting light from the light emitting diode is not absorbed by the opaque substrate, and the light-emitting cell becomes a cell that can emit light in forward, backward and sideward directions, so that the light emitting efficiency of the light-emitting cell is increased. In theory, the light emitting and detecting device, which uses the transparent substrate, should be a high efficiency electro-optics device with the features of emitting and detecting light in forward, backward and sideward directions. However, since there is a limitation of the conventional packaging method, and the electrode on the transparent substrate is still formed by the conventional gilding or surfgold method, the efficiency of light emitting and detecting is only increased on the sidewalls of transparent substrate with the used of the transparent substrate. Therefore, the advantage of the device having the transparent substrate cannot be exerted completely.
As shown in FIG. 1, the die carrier 30 of the light-emitting cell is shown. A lead frame, a printed circuit board, or a header is usually used to be a carrier for packaging, and the die carrier 30 is bonded to the substrate 20 of the light-emitting cell to form the first electrode of the light-emitting cell. The cell-fixing surface 40 between the light-emitting cell and the die carrier 30 is fixed on the die carrier 30 by using silver paste, conductive paste, or eutectic bond. Then, a second electrode 50 upon the light-emitting cell is wire bonded to another point of the lead frame 35. Thereafter, a power source is individually connected to the die carrier 30 and the lead frame 35, so that the epitaxial structure 10 of the light-emitting cell emits light.
As shown in FIG. 2, FIG. 2 is a cross-sectional view of a conventional light-emitting cell fixed on a die carrier, wherein the conventional light-emitting cell has a substrate made of insulating material. If the substrate 70 of the light-emitting cell is made of an insulating material, the process is the same as the one described above. The cell-fixing surface 90 between the light-emitting cell and the die carrier 80 is fixed on the die carrier 80 by using silver paste. Then, a first electrode 92 is wire bonded to the lead frame 85 and the second electrode 94 is wire bonded to the die carrier 80, respectively. Finally, a power source is individually connected to the die carrier 80 and the lead frame 85, and then the epitaxial structure 60 of the light-emitting cell emits light.
However, owing to the light-emitting cell bonded directly on the die carrier, the light generated from the light-emitting cell is absorbed by the conventional cell-fixing surface. Therefore, most of the light emitted through the transparent substrate is absorbed by the cell-fixing surface, although the transparent substrate is utilized to replace the opaque substrate. Thus, the light emitting efficiency is decreased, and the advantage, that the light can be emitted in forward and backward directions from the light-emitting cell with the use of the transparent substrate, cannot be fully performed.
In view of the background of the invention described above, for overcoming the disadvantage, that the light emitting efficiency of the light emitting diode is decreased because the light emitted from the light-emitting cell is absorbed by the cell-fixing surface after the light-emitting cell fixed on the die carrier, the present invention provides a structure and a method for forming an electro-optics device, and more particularly, for forming a high efficiency electro-optics device.
It is the primary object of the present invention to provide a structure and a method for forming a high efficiency electro-optics device. In the present invention, the cell-fixing surface area between the die carrier and the electro-optics cell is decreased, thereby increasing the light emitting and detecting regions of the electro-optics cell. In the meantime, according to the present invention, by using a newly-designed gilding pattern, the light shielding area of the backside of the electro-optics cell is further reduced. Therefore, the light emitting efficiency and the photo detecting sensitivity of the electro-optics device are also increased substantially, so that the electro-optics cell can perform with the maximum efficiency. More particularly, for a device having a transparent substrate, the structure provided by the present invention together with the newly-designed gilding pattern matching with the structure can let the device fully perform, thereby resolving the problem of the low device efficiency.
It is the secondary object of the present invention to provide a structure and a method for forming a high efficiency electro-optics device. With the present invention, a self-aligned bond can be achieved by utilizing the eutectic or the metal-melting method when the electro-optics cell is fixed on the cell-fixing surface. Thus, the accuracy for packaging the device is increased substantially, and the failure therefore is decreased.
In accordance with the aforementioned objects of the present invention, the present invention provides a structure of high efficiency electro-optics device, the structure consisting of: a cell-fixing surface defined on the convex portion of a convex die carrier; an electro-optics cell, located on the cell-fixing surface, the electro-optics cell having a first electrode electrically connected with the convex die carrier and a second electrode electrically connected with another lead frame.
In accordance with the aforementioned objects of this invention, the present invention provides a method for forming a high efficiency electro-optics device, comprising the following steps of: providing a convex die carrier with a convex portion defined as a cell-fixing surface; bonding an electro-optics device cell, which has a first electrode and a second electrode, on the cell-fixing surface; connecting the first electrode electrically with the convex portion of the convex die carrier; and connecting the second electrode electrically with a lead frame.